1. Field of the Invention
The present invention relates to a power supply for supplying high-voltage power to a drive electric motor of a hybrid car or an electric car. Although not limited thereto, the invention has applicability to two-wheeled vehicles.
2. Description of the Related Art
Conventional electrical cars are driven by an electric motor via electric power from a battery. Similarly, hybrid cars are driven via the combination of a gasoline internal combustion engine and an electric motor. In these electric vehicles, as disclosed in, for example, Japanese Publication JP 2005-98251, a high-voltage battery (e.g., 36V) is provided separately from a low-voltage battery (e.g., 12V), and the electric motor is driven by this high-voltage battery.
In order to drive the electric motor efficiently with high output, the voltage of power source battery units has becoming increasingly higher, leading to the adoption of vehicle power supplies in which a plurality of batteries are connected in series to supply high-voltage power on the order of, for example, 300V or 500V.
However, such an increase in power source voltage leads to a corresponding increase in the withstand-voltage performance required of control units or control elements within the power supply system. The power supply system thus becomes more bulky due to the large-scale structure. In other words, the size, weight, and cost of the power supply system increases. Further, the freedom of design is reduced.